318 Mr Horner on the occurrence of the Megalichthys 



tween the supposed fresh-water limestone and the other coal- 

 measures. 



The other sauroid fish, remains of which have been found at 

 Burdiehouse, is the Pygopterus. Now, most of the specimens 

 of this genus of fish which have hitherto been met with, have 

 been derived from strata abounding in marine fossils, viz. the 

 Zechstein of Mansfield and other places in Germany, and the 

 magnesian limestone of the county of Durham ; they have also 

 been found in the coal formation at Saarbrock ;* and M. 

 Agassiz has recognised, in the above mentioned limestone of the 

 coal-measures at Pettycur, a new species which he has named 

 P. Jamesoni. 



" The fish," says Dr Hibbert, " which the limestone en- 

 tombs in far the greatest number, is an individual which I had 

 little difficulty in referring to the genus Palaeoniscus." — P. 190. 

 Now the genus Palaeoniscus is found abundantly in the Zech- 

 stein of Mansfeld, and in the equivalent of that rock in Eng- 

 land, the magnesian limestone at East Thickly in the county 

 of Durham.-f- In this last locality the remains of this fish are 

 associated with vegetable impressions which Professor Sedg- 

 wick refers to the fern tribe,| and with an impure coal. They 

 have been met with, besides, in different coal-formations in 

 England, France, Germany, and the United States ; and three 

 species have been recognised in the limestone of Pettycur, one 

 of which, P. Robisoni, is identical with that which is found in 

 such abundance at Burdiehouse. 



Of the five species of Amblypterus described by Agassiz, 

 four are from the regular coal deposits of Saarbrlick and that 

 neighbourhood, the other being from Brazil, but in what for- 

 mation it is not mentioned. 



The Eurynotus is said by Dr Hibbert, p. 192, to resemble 

 the Platysomus. M. Agassiz describes five different species of 

 the Platysomus, and of these, two were obtained from the 

 Zechstein, and three from the magnesian limestone. He has 

 found a species of Eurynotus in the limestone of Pettycur. 



It appears, therefore, that the fish found in the limestone un- 

 der consideration, in place of being an " ambiguous criterion," 



• Agassiz, Poissons Fossiles. t IbW. 



t Geol. Trans. 2d ser. vol. iii. 



